Pullulan: Microbial sources, production and applications

Chemical transformation of the multibudding yeast, Aureobasidium pullulans

Aureobasidium pullulans is a ubiquitous polymorphic black yeast with industrial and agricultural applications. It has recently gained attention amongst cell biologists for its unconventional mode of proliferation in which multinucleate yeast cells make multiple buds within a single cell cycle. Here, we combine a chemical transformation method with genome-targeted homologous recombination to yield ∼60 transformants/μg of DNA in just 3 days. This protocol is simple, inexpensive, and requires no specialized equipment. We also describe vectors with codon-optimized green and red fluorescent proteins for A. pullulans and use these tools to explore novel cell biology. Quantitative imaging of a strain expressing cytosolic and nuclear markers showed that although the nuclear number varies considerably among cells of similar volume, total nuclear volume scales with cell volume over an impressive 70-fold size range. The protocols and tools described here expand the toolkit for A. pullulans biologists and will help researchers address the many other puzzles posed by this polyextremotolerant and morphologically plastic organism.

Advances in Aureobasidium research: Paving the path to industrial utilization

We here explore the potential of the fungal genus Aureobasidium as a prototype for a microbial chassis for industrial biotechnology in the context of a developing circular bioeconomy. The study emphasizes the physiological advantages of Aureobasidium, including its polyextremotolerance, broad substrate spectrum, and diverse product range, making it a promising candidate for cost-effective and sustainable industrial processes. In the second part, recent advances in genetic tool development, as well as approaches for up-scaled fermentation, are described. This review adds to the growing body of scientific literature on this remarkable fungus and reveals its potential for future use in the biotechnological industry.

Hydrogels Based on Proteins Cross-Linked with Carbonyl Derivatives of Polysaccharides, with Biomedical Applications

Adding carbonyl groups into the hydrogel matrix improves the stability and biocompatibility of the hydrogels, making them suitable for different biomedical applications. In this review article, we will discuss the use of hydrogels based on polysaccharides modified by oxidation, with particular attention paid to the introduction of carbonyl groups. These hydrogels have been developed for several applications in tissue engineering, drug delivery, and wound healing. The review article discusses the mechanism by which oxidized polysaccharides can introduce carbonyl groups, leading to the development of hydrogels through cross-linking with proteins. These hydrogels have tunable mechanical properties and improved biocompatibility. Hydrogels have dynamic properties that make them promising biomaterials for various biomedical applications. This paper comprehensively analyzes hydrogels based on cross-linked proteins with carbonyl groups derived from oxidized polysaccharides, including microparticles, nanoparticles, and films. The applications of these hydrogels in tissue engineering, drug delivery, and wound healing are also discussed.

A structure-functionality insight into the bioactivity of microbial polysaccharides toward biomedical applications: A review

Microbial polysaccharides (MPs) are biopolymers secreted by microorganisms such as bacteria and fungi during their metabolic processes. Compared to polysaccharides derived from plants and animals, MPs have advantages such as wide sources, high production efficiency, and less susceptibility to natural environmental influences. The most attractive feature of MPs lies in their diverse biological activities, such as antioxidative, anti-tumor, antibacterial, and immunomodulatory activities, which have demonstrated immense potential for applications in functional foods, cosmetics, and biomedicine. These bioactivities are precisely regulated by their sophisticated molecular structure. However, the mechanisms underlying this precise regulation are not yet fully understood and continue to evolve. This article presents a comprehensive review of the most representative species of MPs, including their fermentation and purification processes and their biomedical applications in recent years. In particular, this work presents an in-depth analysis into the structure-activity relationships of MPs across multiple molecular levels. Additionally, this review discusses the challenges and prospects of investigating the structure-activity relationships, providing valuable insights into the broad and high-value utilization of MPs.

Green construction of self-floating polysaccharide-based hydrogels with catalytic activity for efficient organic pollutants reduction

This study employed an anionic heteropolysaccharide extracted from overgrown Enteromorpha and homopolysaccharide pullulan to fabricate a self-floating hydrogel by introducing bubble templates. Subsequently, green in-situ reduction and immobilization of silver nanoparticles (Ag NPs) in the hydrogel were successfully achieved without additional reducing agents. The heteropolysaccharide from Enteromorpha provides carboxyl and sulfate groups for Ag+ ions complexation, which is beneficial for the in-situ reduction of Ag NPs and inhibits their aggregation. The incorporation of bubble templates facilitates the creation of a hierarchical pore structure in the hydrogel, giving it self-floating properties for easy recycling, while the hierarchical network with rich anchor sites ensuring adequate traction for Ag NPs dispersion and stabilization. By adjusting polysaccharide content and using bubble templates, Ag NPs smaller than 10 nm can be obtained. The composite hydrogel exhibits tunable catalytic activity and excellent degradation towards Rhodamine B, Methyl Orange, and 4-Nitrophenol, with the normalized rate constant (knor) of 78.89, 59.08, and 30.42 min-1 g-1, respectively. Notably, the reduction efficiency remained above 98 % after 6 recycles with little leaching of Ag NPs, benefiting from its self-floating ability for easy recovery in practical applications.

Optimization of pullulan production by Aureobasidium pullulans using semi-solid-state fermentation and artificial neural networks: Characterization and antibacterial activity of pullulan impregnated with Ag-TiO2 nanocomposite

This study presents a novel and efficient approach for pullulan production using artificial neural networks (ANNs) to optimize semi-solid-state fermentation (S-SSF) on faba bean biomass (FBB). This method achieved a record-breaking pullulan yield of 36.81 mg/g within 10.82 days, significantly exceeding previous results. Furthermore, the study goes beyond yield optimization by characterizing the purified pullulan, revealing its unique properties including thermal stability, amorphous structure, and antioxidant activity. Energy-dispersive X-ray spectroscopy and scanning electron microscopy confirmed its chemical composition and distinct morphology. This research introduces a groundbreaking combination of ANNs and comprehensive characterization, paving the way for sustainable and cost-effective pullulan production on FBB under S-SSF conditions. Additionally, the study demonstrates the successful integration of pullulan with Ag@TiO2 nanoparticles during synthesis using Fusarium oxysporum. This novel approach significantly enhances the stability and efficacy of the nanoparticles by modifying their surface properties, leading to remarkably improved antibacterial activity against various human pathogens. These findings showcase the low-cost production medium, and extensive potential of pullulan not only for its intrinsic properties but also for its ability to significantly improve the performance of nanomaterials. This breakthrough opens doors to diverse applications in various fields.

Understanding exopolysaccharide byproduct formation in Komagataella phaffii fermentation processes for recombinant protein production

BACKGROUND

Komagataella phaffii (Pichia pastoris) has emerged as a common and robust biotechnological platform organism, to produce recombinant proteins and other bioproducts of commercial interest. Key advantage of K. phaffii is the secretion of recombinant proteins, coupled with a low host protein secretion. This facilitates downstream processing, resulting in high purity of the target protein. However, a significant but often overlooked aspect is the presence of an unknown polysaccharide impurity in the supernatant. Surprisingly, this impurity has received limited attention in the literature, and its presence and quantification are rarely addressed.

RESULTS

This study aims to quantify this exopolysaccharide in high cell density recombinant protein production processes and identify its origin. In stirred tank fed-batch fermentations with a maximal cell dry weight of 155 g/L, the polysaccharide concentration in the supernatant can reach up to 8.7 g/L. This level is similar to the achievable target protein concentration. Importantly, the results demonstrate that exopolysaccharide production is independent of the substrate and the protein production process itself. Instead, it is directly correlated with biomass formation and proportional to cell dry weight. Cell lysis can confidently be ruled out as the source of this exopolysaccharide in the culture medium. Furthermore, the polysaccharide secretion can be linked to a mutation in the HOC1 gene, featured by all derivatives of strain NRRL Y-11430, leading to a characteristic thinner cell wall.

CONCLUSIONS

This research sheds light on a previously disregarded aspect of K. phaffii fermentations, emphasizing the importance of monitoring and addressing the exopolysaccharide impurity in biotechnological applications, independent of the recombinant protein produced.

Nutritive profile, pharmaceutical potentials, and structural analysis of multifunctional bioactive fungal polysaccharides-A review

Asian nations have long used edible fungi as food and medicine. Polysaccharides are among the main building units of the cell walls of fungi. Fungal polysaccharides have been documented in the medicinal and industrial sectors as products with a vast array of various biological activities and applications such as antitumor, antioxidant, anticancer, immunomodulation, and antiviral activities, etc. The goal of this review is to give insights into the various biological activities of mushroom polysaccharides and their potential as a medicine for human health. The extraction, purity, and structural analysis of fungal polysaccharides were also reviewed in this work. Also, future prospective, and challenges for fungal polysaccharides in pharmaceutical applications can be found in this review. Overall, this review serves as a valuable resource in exploring the therapeutic potential and applications of fungal polysaccharides. By building upon the existing knowledge base and addressing critical research gaps, researchers can find new opportunities for utilizing fungal polysaccharides as valuable therapeutic agents and functional ingredients in pharmaceuticals, nutraceuticals, and biotechnology.

Clinical and Preclinical Methods of Heat-Stabilization of Human Vaccines

Vaccines have historically faced challenges regarding stability, especially in regions lacking a robust cold chain infrastructure. This review delves into established and emergent techniques to improve the thermostability of vaccines. We discuss the widely practiced lyophilization method, effectively transforming liquid vaccine formulations into a solid powdered state, enhancing storage and transportation ability. However, potential protein denaturation during lyophilization necessitates alternative stabilization methods. Cryoprotectants, namely, starch and sugar molecules, have shown promise in protecting vaccine antigens and adjuvants from denaturation and augmenting the stability of biologics during freeze-drying. Biomineralization, a less studied yet innovative approach, utilizes inorganic or organic-inorganic hybrids to encapsulate biological components of vaccines with a particular emphasis on metal-organic coordination polymers. Encapsulation in organic matrices to form particles or microneedles have also been studied in the context of vaccine thermostability, showing some ability to store outside the cold-chain. Unfortunately, few of these techniques have advanced to clinical trials that evaluate differences in storage conditions. Nonetheless, early trials suggest that alternative storage techniques are viable and emphasize the need for more comprehensive studies. This review underscores the pressing need for heat-stable vaccines, especially in light of the increasing global distribution challenges. Combining traditional methods with novel approaches holds promise for the future adaptability of vaccine distribution and use.

Exploring polysaccharide-based bio-adhesive topical film as a potential platform for wound dressing application: A review

Wound dressings act as a physical barrier between the wound site and the external environment, preventing additional harm; choosing suitable wound dressings is essential for the healing process. Polysaccharide biopolymers have demonstrated encouraging findings and therapeutic prospects in recent decades about wound therapy. Additionally, polysaccharides have bioactive qualities like anti-inflammatory, antibacterial, and antioxidant capabilities that can help the process of healing. Due to their excellent tissue adhesion, swelling, water absorption, bactericidal, and immune-regulating properties, polysaccharide-based bio-adhesive films have recently been investigated as intriguing alternatives in wound management. These films also mimic the structure of the skin and stimulate the regeneration of the skin. This review presented several design standards and functions of suitable bio-adhesive films for the healing of wounds. Additionally, the most recent developments in the use of bio-adhesive films as wound dressings based on polysaccharides, including hyaluronic acid, chondroitin sulfate, dextran, alginate, chitosan, cellulose, konjac glucomannan, gellan gum, xanthan gum, pectin, guar gum, heparin, arabinogalactans, carrageen, and tragacanth gum, are thoroughly discussed. Lastly, to create a road map for the function of polysaccharide-based bio-adhesive films in advanced wound care, their clinical performances and future challenges in making bio-adhesive films by three-dimensional bioprinting are summarized.

Stimuli responsiveness of recent biomacromolecular systems (concept to market): A review

Stimuli responsive delivery systems, also known as smart/intelligent drug delivery systems, are specialized delivery vehicles designed to provide spatiotemporal control over drug release at target sites in various diseased conditions, including tumor, inflammation and many others. Recent advances in the design and development of a wide variety of stimuli-responsive (pH, redox, enzyme, temperature) materials have resulted in their widespread use in drug delivery and tissue engineering. The aim of this review is to provide an insight of recent nanoparticulate drug delivery systems including polymeric nanoparticles, dendrimers, lipid-based nanoparticles and the design of new polymer-drug conjugates (PDCs), with a major emphasis on natural along with synthetic commercial polymers used in their construction. Special focus has been placed on stimuli-responsive polymeric materials, their preparation methods, and the design of novel single and multiple stimuli-responsive materials that can provide controlled drug release in response a specific stimulus. These stimuli-sensitive drug nanoparticulate systems have exhibited varying degrees of substitution with enhanced in vitro/in vivo release. However, in an attempt to further increase drug release, new dual and multi-stimuli based natural polymeric nanocarriers have been investigated which respond to a mixture of two or more signals and are awaiting clinical trials. The translation of biopolymeric directed stimuli-sensitive drug delivery systems in clinic demands a thorough knowledge of its mechanism and drug release pattern in order to produce affordable and patient friendly products.

Exploring the potential of pullulan-based films and coatings for effective food preservation: A comprehensive analysis of properties, activation strategies and applications

Pullulan is naturally occurring polysaccharide exhibited potential applications for food preservation has gained increasing attention over the last half-century. Recent studies focused on efficient preservation and targeted inhibition using active composite ingredients and advanced technologies. This has led to the emergence of pullulan-based biofilm preservation. This review extensively studied the characteristics of pullulan-based films and coatings, including their mechanical strength, water vapor permeability, thermal stability, and potential as a microbial agent. Furthermore, the distinct characteristics of pullulan, production methods, and activation strategies, such as pullulan derivatization, various compounded ingredients (plant extracts, microorganisms, and animal additives), and other technologies (e.g., ultrasound), are thoroughly studied for the functional property enhancement of pullulan-based films and coatings, ensuring optimal preservation conditions for diverse food products. Additionally, we explore hypotheses that further illuminate pullulan's potential as an eco-friendly bioactive material for food packaging applications. In addition, this review evaluates various methods to improve the efficiency of the film-forming mechanism, such as improving the direct coating process, bioactive packaging films, and implementing layer-by-layer coatings. Finally, current analyses put forward suggestions for future advancement in pullulan-based bioactive films, with the aim of expanding their range of potential applications.

Use of Aureobasidium in a sustainable economy

Aureobasidium is omnipresent and can be isolated from air, water bodies, soil, wood, and other plant materials, as well as inorganic materials such as rocks and marble. A total of 32 species of this fungal genus have been identified at the level of DNA, of which Aureobasidium pullulans is best known. Aureobasidium is of interest for a sustainable economy because it can be used to produce a wide variety of compounds, including enzymes, polysaccharides, and biosurfactants. Moreover, it can be used to promote plant growth and protect wood and crops. To this end, Aureobasidium cells adhere to wood or plants by producing extracellular polysaccharides, thereby forming a biofilm. This biofilm provides a sustainable alternative to petrol-based coatings and toxic chemicals. This and the fact that Aureobasidium biofilms have the potential of self-repair make them a potential engineered living material avant la lettre. KEY POINTS: •Aureobasidium produces products of interest to the industry •Aureobasidium can stimulate plant growth and protect crops •Biofinish of A. pullulans is a sustainable alternative to petrol-based coatings •Aureobasidium biofilms have the potential to function as engineered living materials.

Fast insights into chitosan-cleaving enzymes by simultaneous analysis of polymers and oligomers through size exclusion chromatography

The thorough characterization of chitosan-cleaving enzymes is crucial to unveil structure-function relationships of this promising class of biomolecules for both, enzymatic fingerprinting analyses and to use the enzymes as biotechnological tools to produce tailor-made chitosans for diverse applications. Analyzing polymeric substrates as well as oligomeric products has been established as an effective way to understand the actions of enzymes, but it currently requires separate, rather laborious methods to obtain the full picture. Here, we present ultra high performance size exclusion chromatography coupled to refractive index and mass spectrometry detection (UHPSEC-RI-MS) as a straightforward method for the semi-quantitative analysis of chitosan oligomers of up to ten monomers in length. Additionally, the method allows to determine the average molecular weight of the remaining polymers and its distribution. By sampling live from an ongoing enzymatic reaction, UHPSEC-RI-MS offers the unique opportunity to analyze polymers and oligomers simultaneously-i.e., to monitor the molecular weight reduction of the polymeric substrate over the course of the digestion, while at the same time analyzing the emerging oligomeric products in a semi-quantitative manner. In this way, a single simple analysis yields detailed insights into an enzyme's action on a given substrate.

The Ruminococcus bromii amylosome protein Sas6 binds single and double helical α-glucan structures in starch

Resistant starch is a prebiotic accessed by gut bacteria with specialized amylases and starch-binding proteins. The human gut symbiont Ruminococcus bromii expresses Sas6 (Starch Adherence System member 6), which consists of two starch-specific carbohydrate-binding modules from family 26 (RbCBM26) and family 74 (RbCBM74). Here, we present the crystal structures of Sas6 and of RbCBM74 bound with a double helical dimer of maltodecaose. The RbCBM74 starch-binding groove complements the double helical α-glucan geometry of amylopectin, suggesting that this module selects this feature in starch granules. Isothermal titration calorimetry and native mass spectrometry demonstrate that RbCBM74 recognizes longer single and double helical α-glucans, while RbCBM26 binds short maltooligosaccharides. Bioinformatic analysis supports the conservation of the amylopectin-targeting platform in CBM74s from resistant-starch degrading bacteria. Our results suggest that RbCBM74 and RbCBM26 within Sas6 recognize discrete aspects of the starch granule, providing molecular insight into how this structure is accommodated by gut bacteria.

Bioinspired Zn-MOF doped radial porous chitosan-based sponge with antibacterial and antioxidant properties for rapid hemostasis and wound healing

Herein, a novel bioinspired radial porous zinc-based metal-organic framework (Zn-MOF) doped sodium alginate/chitosan derivatives/pullulan-based SA/PSCS/Pul/Zn-MOF (SPCP/Zn) composites sponge with excellent antioxidant and antibacterial properties was fabricated by the ice-templating method. Boric acid (BA) and Ca2+, which were respectively used as hydrogen- and ionic- bonding cross-linkers, provided strong mechanical properties for sponge matrix composed of SA, PSCS, and Pul. The obtained SPCP/Zn sponge exhibited uniform porous morphology, proper hydrophilicity, and admirable biocompatibility. In addition, the SPCP/Zn sponge achieved a sustained release of Zn2+ and gallic acid, which displayed powerful antibacterial and antioxidant activities. Importantly, the SPCP/Zn sponge exhibited shorter rapid hemostasis (20.4 ± 2.9 s) and lower blood loss (19.8 ± 4.3 mg). The SPCP/Zn sponge also showed faster wound closure ratio for the rat full-thickness skin defect model. It was revealed that SPCP/Zn sponge could significantly accelerate and enhance wound healing through downregulating inflammatory cytokines (TNF-α, IL-6) and increasing the expression of growth factors (VEGF). Due to its excellent properties, the SPCP/Zn sponge may have promising potential in wound healing applications.

A Novel Fabrication of Heterogeneous Saponified Poly(Vinyl Alcohol)/Pullulan Blend Film for Improved Wound Healing Application

In this study, a novel film of poly(vinyl alcohol) (PVA)/pullulan (PULL) with improved surface characteristics was prepared from poly(vinyl acetate) (PVAc)/PULL blend films with various mass ratios after the saponification treatment in a heterogeneous medium. According to proton nuclear magnetic resonance (1H-NMR), Fourier transform infrared, and X-ray diffraction results, it was established that the successful fabrication of saponified PVA/PULL (100/0, 90/10, and 80/20) films could be obtained from PVAc/PULL (100/0, 90/10, and 80/20) films, respectively, after 72 h saponification at 50 °C. The degree of saponification calculated from 1H-NMR analysis results showed that fully saponified PVA was obtained from all studied films. Improved hydrophilic characteristics of the saponified films were revealed by a water contact angle test. Moreover, the saponified films showed improved mechanical behavior, and the micrographs of saponified films showed higher surface roughness than the unsaponified films. This kind of saponified film can be widely used for biomedical applications. Moreover, the reported saponified film dressing extended the lifespan of dressing as determined by its self-healing capacity and considerably advanced in vivo wound-healing development, which was attributed to its multifunctional characteristics, meaning that saponified film dressings are promising candidates for full-thickness skin wound healing.

Exploring the diverse applications of Carbohydrate macromolecules in food, pharmaceutical, and environmental technologies

Carbohydrates are a class of macromolecules that has significant potential across several domains, including the organisation of genetic material, provision of structural support, and facilitation of defence mechanisms against invasion. Their molecular diversity enables a vast array of essential functions, such as energy storage, immunological signalling, and the modification of food texture and consistency. Due to their rheological characteristics, solubility, sweetness, hygroscopicity, ability to prevent crystallization, flavour encapsulation, and coating capabilities, carbohydrates are useful in food products. Carbohydrates hold potential for the future of therapeutic development due to their important role in sustained drug release, drug targeting, immune antigens, and adjuvants. Bio-based packaging provides an emerging phase of materials that offer biodegradability and biocompatibility, serving as a substitute for traditional non-biodegradable polymers used as coatings on paper. Blending polyhydroxyalkanoates (PHA) with carbohydrate biopolymers, such as starch, cellulose, polylactic acid, etc., reduces the undesirable qualities of PHA, such as crystallinity and brittleness, and enhances the PHA's properties in addition to minimizing manufacturing costs. Carbohydrate-based biopolymeric nanoparticles are a viable and cost-effective way to boost agricultural yields, which is crucial for the increasing global population. The use of biopolymeric nanoparticles derived from carbohydrates is a potential and economically viable approach to enhance the quality and quantity of agricultural harvests, which is of utmost importance given the developing global population. The carbohydrate biopolymers may play in plant protection against pathogenic fungi by inhibiting spore germination and mycelial growth, may act as effective elicitors inducing the plant immune system to cope with pathogens. Furthermore, they can be utilised as carriers in controlled-release formulations of agrochemicals or other active ingredients, offering an alternative approach to conventional fungicides. It is expected that this review provides an extensive summary of the application of carbohydrates in the realms of food, pharmaceuticals, and environment.

The reduce of water vapor permeability of polysaccharide-based films in food packaging: A comprehensive review

Polysaccharide-based films are favored in the food packaging industry because of their advantages of green and safe characters, as well as natural degradability, but due to the structural defects of polysaccharides, they also have the disadvantages of high water vapor permeability (WVP), which greatly limits their application in the food packaging industry. To break the limitation, numerous methods, e.g., physical and/or chemical methods, have been employed. This review mainly elaborates the up-to-date research status of the application of polysaccharide-based films (PBFs) in food packaging area, including various films from cellulose and its derivatives, starch, chitosan, pectin, alginate, pullulan and so on, while the methods of reducing the WVP of PBFs, mainly divided into physical and chemical methods, are summarized, as well as the discussions about the existing problems and development trends of PBFs. In the end, suggestions about the future development of WVP of PBFs are presented.

Regulation of cell differentiation to promote pullulan synthesis in Aureobasidium pullulans NG

Pullulan is a polymer produced by Aureobasidium spp. The yield of pullulan production can be impacted by the cellular differentiation of Aureobasidium spp., which changes with alterations in the growth environment. To improve pullulan yield, identifying key factors that regulate cellular differentiation is crucial. In this study, the main form of pullulan synthesis in Aureobasidium pullulans NG was through swollen cells (SC). The results showed that citric acid (CA) can regulate the cellular differentiation of Aureobasidium pullulans NG by accumulating higher levels of CA in the cells to maintain growth in SC form and increase pullulan production. The addition of 1.0% CA to Aureobasidium pullulans NG for 96 h resulted in a significant increase in pullulan production, producing 18.32 g/l compared to the control group which produced 10.23 g/l. Our findings suggest that controlling cellular differentiation using CA is a promising approach for enhancing pullulan production in Aureobasidium pullulans. KEY POINTS: • The regulation of cell differentiation in Aureobasidium pullulans NG is demonstrated to be influenced by citric acid. • Intracellular citric acid levels in Aureobasidium pullulans NG have been shown to support the growth of swollen cells. • Citric acid has been found to increase pullulan production in Aureobasidium pullulans NG.

Traversing the diverse avenues of exopolysaccharides-based nanocarriers in the management of cancer

Exopolysaccharides are unique polymers generated by living organisms such as algae, fungi and bacteria to protect them from environmental factors. After a fermentative process, these polymers are extracted from the medium culture. Exopolysaccharides have been explored for their anti-viral, anti-bacterial, anti-tumor, and immunomodulatory effects. Specifically, they have acquired massive attention in novel drug delivery strategies owing to their indispensable properties like biocompatibility, biodegradability, and lack of irritation. Exopolysaccharides such as dextran, alginate, hyaluronic acid, pullulan, xanthan gum, gellan gum, levan, curdlan, cellulose, chitosan, mauran, and schizophyllan exhibited excellent drug carrier properties. Specific exopolysaccharides, such as levan, chitosan, and curdlan, have demonstrated significant antitumor activity. Moreover, chitosan, hyaluronic acid and pullulan can be employed as targeting ligands decorated on nanoplatforms for effective active tumor targeting. This review shields light on the classification, unique characteristics, antitumor activities and nanocarrier properties of exopolysaccharides. In addition, in vitro human cell line experiments and preclinical studies associated with exopolysaccharide-based nanocarriers have also been highlighted.

Production and applications of pullulan from lignocellulosic biomass: Challenges and perspectives

Pullulan is an exopolysaccharide produced by Aureobasidium pullulans, with interesting characteristics which lead to its application in industries such as pharmaceuticals, cosmetics, food, and others. To reduce production costs for industrial applications, cheaper raw materials such as lignocellulosic biomass can be utilized as a carbon and nutrient source for the microbial process. In this study, a comprehensive and critical review was conducted, encompassing the pullulan production process and the key influential variables. The main properties of the biopolymer were presented, and different applications were discussed. Subsequently, the utilization of lignocellulosics for pullulan production within the framework of a biorefinery concept was explored, considering the main published works that deal with materials such as sugarcane bagasse, rice husk, corn straw, and corn cob. Next, the main challenges and future prospects in this research area were highlighted, indicating the key strategies to favor the industrial production of pullulan from lignocellulosic biomasses.

Pullulanase: unleashing the power of enzyme with a promising future in the food industry

Pullulanases are the most important industrial group of enzymes in family 13 glycosyl hydrolases. They hydrolyze either α-1,6 and α-1,4 or both glycosidic bonds in pullulan as well as other carbohydrates to produce glucose, maltose, and maltotriose syrups, which have important uses in food and other related sectors. However, very less reports are available on pullulanase production from native strains because of low yield issues. In line with the increasing demands for pullulanase, it has become important to search for novel pullulanase-producing microorganisms with high yields. Moreover, high production costs and low yield are major limitations in the industrial production of pullulanase enzymes. The production cost of pullulanase by using the solid-state fermentation (SSF) process can be minimized by selecting agro-industrial waste. This review summarizes the types, sources, production strategies, and potential applications of pullulanase in different food and other related industries. Researchers should focus on fungal strains producing pullulanase for better yield and low production costs by using agro-waste. It will prove a better enzyme in different food processing industries and will surely reduce the cost of products.

Polymeric Based Hydrogel Membranes for Biomedical Applications

The development of biomedical applications is a transdisciplinary field that in recent years has involved researchers from chemistry, pharmacy, medicine, biology, biophysics, and biomechanical engineering. The fabrication of biomedical devices requires the use of biocompatible materials that do not damage living tissues and have some biomechanical characteristics. The use of polymeric membranes, as materials meeting the above-mentioned requirements, has become increasingly popular in recent years, with outstanding results in tissue engineering, for regeneration and replenishment of tissues constituting internal organs, in wound healing dressings, and in the realization of systems for diagnosis and therapy, through the controlled release of active substances. The biomedical application of hydrogel membranes has had little uptake in the past due to the toxicity of cross-linking agents and to the existing limitations regarding gelation under physiological conditions, but now it is proving to be a very promising field This review presents the important technological innovations that the use of membrane hydrogels has promoted, enabling the resolution of recurrent clinical problems, such as post-transplant rejection crises, haemorrhagic crises due to the adhesion of proteins, bacteria, and platelets on biomedical devices in contact with blood, and poor compliance of patients undergoing long-term drug therapies.

Designing starch derivatives with desired structures and functional properties via rearrangements of glycosidic linkages by starch-active transglycosylases

Modification of starch by transglycosylases from glycoside hydrolase families has attracted much attention recently; these enzymes can produce starch derivatives with novel properties, i.e. processability and functionality, employing highly efficient and safe methods. Starch-active transglycosylases cleave starches and transfer linear fragments to acceptors introducing α-1,4 and/or linear/branched α-1,6 glucosidic linkages, resulting in starch derivatives with excellent properties such as complexing and resistance to digestion characteristics, and also may be endowed with new properties such as thermo-reversible gel formation. This review summarizes the effects of variations in glycosidic linkage composition on structure and properties of modified starches. Starch-active transglycosylases are classified into 4 groups that form compounds: (1) in cyclic with α-1,4 glucosidic linkages, (2) with linear chains of α-1,4 glucosidic linkages, (3) with branched α-1,6 glucosidic linkages, and (4) with linear chains of α-1,6 glucosidic linkages. We discuss potential processability and functionality of starch derivatives with different linkage combinations and structures. The changes in properties caused by rearrangements of glycosidic linkages provide guidance for design of starch derivatives with desired structures and properties, which promotes the development of new starch products and starch processing for the food industry.

Biopharmaceutical applications of microbial polysaccharides as materials: A review

Biological characteristics of natural polymers make microbial polysaccharides an excellent choice for biopharmaceuticals. Due to its easy purifying procedure and high production efficiency, it is capable of resolving the existing application issues associated with some plant and animal polysaccharides. Furthermore, microbial polysaccharides are recognized as prospective substitutes for these polysaccharides based on the search for eco-friendly chemicals. In this review, the microstructure and properties of microbial polysaccharides are utilized to highlight their characteristics and potential medical applications. From the standpoint of pathogenic processes, in-depth explanations are provided on the effects of microbial polysaccharides as active ingredients in the treatment of human diseases, anti-aging, and drug delivery. In addition, the scholarly developments and commercial applications of microbial polysaccharides as medical raw materials are also discussed. The conclusion is that understanding the use of microbial polysaccharides in biopharmaceuticals is essential for the future development of pharmacology and therapeutic medicine.

Pullulan in pharmaceutical and cosmeceutical formulations: A review

Pullulan, an α-glucan polysaccharide, is colorless, odorless, non-toxic, non-carcinogenic, highly biocompatible, edible and biodegradable in nature. The long chains of glucopyranose rings in pullulan structure are linked together by α-(1 → 4) and α-(1 → 6) glycosidic linkages. The occurrence of both glycosidic linkages in the pullulan structure contributes to its distinctive properties. The unique structure of pullulan makes it a potent candidate for both pharmaceutical and cosmeceutical applications. In pharmaceuticals, it can be used as a drug carrier and in various dosage formulations. It has been widely used in drug targeting, implants, ocular dosage forms, topical formulations, oral dosage forms, and oral liquid formulations, etc. Pullulan can be used as a potential carrier of active ingredients and their site-specific delivery to skin layers for cosmeceutical applications. It has been extensively used in cosmeceutical formulations like creams, shampoo, lotions, sunscreen, facial packs, etc. The current review highlights applications of pullulan in pharmaceutical and cosmeceutical applications.

Exclusive Biosynthesis of Pullulan Using Taguchi’s Approach and Decision Tree Learning Algorithm by a Novel Endophytic Aureobasidium pullulans Strain

Pullulan is a biodegradable, renewable, and environmentally friendly hydrogel biopolymer, with potential uses in food, medicine, and cosmetics. New endophytic Aureobasidium pullulans (accession number; OP924554) was used for the biosynthesis of pullulan. Innovatively, the fermentation process was optimized using both Taguchi’s approach and the decision tree learning algorithm for the determination of important variables for pullulan biosynthesis. The relative importance of the seven tested variables that were obtained by Taguchi and the decision tree model was accurate and followed each other’s, confirming the accuracy of the experimental design. The decision tree model was more economical by reducing the quantity of medium sucrose content by 33% without a negative reduction in the biosynthesis of pullulan. The optimum nutritional conditions (g/L) were sucrose (60 or 40), K2HPO4 (6.0), NaCl (1.5), MgSO4 (0.3), and yeast extract (1.0) at pH 5.5, and short incubation time (48 h), yielding 7.23% pullulan. The spectroscopic characterization (FT-IR and 1H-NMR spectroscopy) confirmed the structure of the obtained pullulan. This is the first report on using Taguchi and the decision tree for pullulan production by a new endophyte. Further research is encouraged for additional studies on using artificial intelligence to maximize fermentation conditions.

Biofabrication of Functional Pullulan by Aureobasidium pullulans under the Effect of Varying Mineral Salts and Sugar Stress Conditions

Pullulan is a linear exopolysaccharide, produced in the fermentation media of Aureobasidium pullulans, with a variety of applications in the food and pharmaceutical industries. Pullulan derivatives have growing potential for biomedical applications, but the high cost of pullulan biofabrication currently restricts its commercial use. Better control over pullulan yield, molecular weight and melanin production by altering fermentation conditions could improve the economics. In this study, the effects of sugar and mineral salt stresses on the pullulan production of A. pullulans ATCC 42023 were examined in batch processes. The chemical structure of the recovered pullulan was characterized by FTIR and NMR spectroscopy, and the molecular weight distribution was obtained via SEC. Pullulan yield and melanin production varied when the conditions were adjusted, and pullulans with different molar masses were obtained. Higher-yield pullulan production and a lower polydispersity index were observed when CuSO4 was added to the fermentation in comparison with the control and with the addition of sugars and other salts. Biofabrication of pullulan under stress conditions is a promising strategy to enhance biopolymer yield and to obtain pullulan with a targeted molecular weight.

Cationic Pullulan Derivatives Based Flocculants for Removal of Some Metal Oxides from Simulated Wastewater

Modified polysaccharides have been increasingly used as flocculants in wastewater treatment due to their non-toxicity, low price, biodegradability, etc. However, the pullulan derivatives are less used in wastewater purification processes. Therefore, this article presents some data regarding FeO and TiO₂ particle removal from model suspensions by some pullulan derivatives with pendant quaternary ammonium salt groups, trimethylammonium propyl carbamate chloride (TMAP_x-P). The influence of the polymer ionic content, dose, and initial solution concentration as well as of the dispersion pH and composition (metal oxide content, salts, and kaolin) on the separation efficacy were considered. UV-Vis spectroscopy measurements have shown a very good removal efficacy of TMAP_x-P for the FeO particles (around 95% and more), irrespective of the polymer and suspension characteristics; a lower clarification of the TiO₂ particles suspension (removal efficiency between 68% and 75%) was noticed. Both the zeta potential and the particle aggregates size measurements revealed the charge patch as the main mechanism which governs the metal oxide removal process. The surface morphology analysis/EDX data provided supplementary evidence regarding the separation process. A good removal efficiency (90%) of the pullulan derivatives/FeO flocs for the Bordeaux mixture particles from simulated wastewater was found.

High-level production of pullulan from high concentration of glucose by mutagenesis and adaptive laboratory evolution of Aureobasidium pullulans

The cost of carbon sources and the low efficiency of the fermentation titer limit the industrial application of pullulan. In this study, a hypertonic-tolerant strain with efficient utilization of glucose was obtained using a double strategy. Initially, a strain for efficient synthesis of pullulan from glucose was generated by mutagenesis. Subsequently, the mutant was directionally evolved on the plate containing a high glucose concentration to enhance high osmotic resistance. The enzyme activities and the transcriptional levels involved in pullulan biosynthesis and high osmotic tolerance in mutants were increased. Nitrogen source and inorganic salts also significantly affected the production of pullulan by M233-20 from high concentration of glucose. The pullulan titer of 162.1 g/L was obtained using the response surface methodology in the flask. The strain M233-20 produced 162.3 g/L pullulan in a 30-L bioreactor with a yield of 0.82 g/g glucose. Hence, this work provides a potential industrial pullulan producer M233-20 and a strategy to develop excellent strain.

Exopolysaccharides of Fungal Origin: Properties and Pharmaceutical Applications

Fungal exopolysaccharides (EPSs) represent an important group of bioactive compounds secreted by fungi. These biopolymers can be utilized individually or in combination with different bioactive substances for a broad range of pharmaceutical field applications, due to their various biological activities, such as antioxidant, antimicrobial, anti-inflammatory, antiviral, anti-diabetic, and anticoagulant effects. The paper presents an up-to-date review of the main fungal polysaccharides (pullulan, schizophyllan, scleroglucan, botryosphaeran, lentinan, grifolan, and lasiodiplodan), highlighting their structures, producing strains, and useful properties in a double position, as controlled release (rate and selectively targeting) drug carriers, but mostly as active immunomodulating and antitumor compounds in cancer therapy.

Delivery of streptomycin to the rat colon by use of electrospun nanofibers

Drug-loaded electrospun nanofibers are potential drug carrier systems that may optimize disease treatment while reducing the impact on commensal microbes. The feasibility of streptomycin-loaded pullulan nanofibers fabricated from a green electrospinning procedure using water as the solvent was assessed. We conducted a rat study including a group treated with streptomycin-loaded nanofibers (STR-F, n = 5), a group treated with similar concentrations of streptomycin in the drinking water (STR-W, n = 5), and a non-treated control group (CTR, n = 5). Streptomycin was successfully loaded into nanofibers and delivered by this vehicle, which minimized the quantity of the drug released in the ileal compartment of the gut. Ingested streptomycin-resistant E. coli colonized of up to 10⁶ CFU/g feces, revealing a selective effect of streptomycin even when given in the low amounts allowed by the nanofiber-based delivery. 16S amplicon sequencing of the indigenous microbiota revealed differential effects in the three groups. An increase of Peptostreptococcaceae in the cecum of STR-F animals may indicate that the fermentation of nanofibers directly or indirectly promoted growth of bacteria within this family. Our results elucidate relevant properties of electrospun nanofibers as a novel vehicle for delivery of antimicrobials to the large intestine.

Microbial polysaccharides: An emerging family of natural biomaterials for cancer therapy and diagnostics

Microbial polysaccharides (MPs) offer immense diversity in structural and functional properties. They are extensively used in advance biomedical science owing to their superior biodegradability, hemocompatibility, and capability to imitate the natural extracellular matrix microenvironment. Ease in tailoring, inherent bio-activity, distinct mucoadhesiveness, ability to absorb hydrophobic drugs, and plentiful availability of MPs make them prolific green biomaterials to overcome the significant constraints of cancer chemotherapeutics. Many studies have demonstrated their application to obstruct tumor development and extend survival through immune activation, apoptosis induction, and cell cycle arrest by MPs. Synoptic investigations of MPs are compulsory to decode applied basics in recent inclinations towards cancer regimens. The current review focuses on the anticancer properties of commercially available and newly explored MPs, and outlines their direct and indirect mode of action. The review also highlights cutting-edge MPs-based drug delivery systems to augment the specificity and efficiency of available chemotherapeutics, as well as their emerging role in theranostics.

A comprehensive review on recent advances in preparation, physicochemical characterization, and bioengineering applications of biopolymers

Biopolymers are mainly the polymers which are created or obtained from living creatures such as plants and bacteria rather than petroleum, which has traditionally been the source of polymers. Biopolymers are chain-like molecules composed of repeated chemical blocks derived from renewable resources that may decay in the environment. The usage of biomaterials is becoming more popular as a means of reducing the use of non-renewable resources and reducing environmental pollution produced by synthetic materials. Biopolymers' biodegradability and non-toxic nature help to maintain our environment clean and safe. This study discusses how to improve the mechanical and physical characteristics of biopolymers, particularly in the realm of bioengineering. The paper begins with a fundamental introduction and progresses to a detailed examination of synthesis and a unique investigation of several recent focused biopolymers with mechanical, physical, and biological characterization. Biopolymers' unique non-toxicity, biodegradability, biocompatibility, and eco-friendly features are boosting their applications, especially in bioengineering fields, including agriculture, pharmaceuticals, biomedical, ecological, industrial, aqua treatment, and food packaging, among others, at the end of this paper. The purpose of this paper is to provide an overview of the relevance of biopolymers in smart and novel bioengineering applications.

Graphical abstract

The Graphical abstract represents the biological sources and applications of biopolymers. Plants, bacteria, animals, agriculture wastes, and fossils are all biological sources for biopolymers, which are chemically manufactured from biological monomer units, including sugars, amino acids, natural fats and oils, and nucleotides. Biopolymer modification (chemical or physical) is recognized as a crucial technique for modifying physical and chemical characteristics, resulting in novel materials with improved capabilities and allowing them to be explored to their full potential in many fields of application such as tissue engineering, drug delivery, agriculture, biomedical, food industries, and industrial applications.

Linking lifestyle and foraging strategies of marine bacteria: selfish behaviour of particle-attached bacteria in the northern Adriatic Sea

Microbe-mediated enzymatic hydrolysis of organic matter entails the production of hydrolysate, the recovery of which may be more or less efficient. The selfish uptake mechanism, recently discovered, allows microbes to hydrolyze polysaccharides and take up large oligomers, which are then degraded in the periplasmic space. By minimizing the hydrolysate loss, selfish behaviour may be profitable for free-living cells dwelling in a patchy substrate landscape. However, selfish uptake seems to be tailored to algal-derived polysaccharides, abundant in organic particles, suggesting that particle-attached microbes may use this strategy. We tracked selfish polysaccharides uptake in surface microbial communities of the northeastern Mediterranean Sea, linking the occurrence of this processing mode with microbial lifestyle. Additionally, we set up fluorescently labelled polysaccharides incubations supplying phytodetritus to investigate a 'pioneer' scenario for particle-attached microbes. Under both conditions, selfish behaviour was almost exclusively carried out by particle-attached microbes, suggesting that this mechanism may represent an advantage in the race for particle exploitation. Our findings shed light on the selfish potential of particle-attached microbes, suggesting multifaceted foraging strategies exerted by particle colonizers.

Glycyrrhetinic acid-cyclodextrin grafted pullulan nanoparticles loaded doxorubicin as a liver targeted delivery carrier

In this work, glycyrrhetinic acid (GA)-β-cyclodextrin grafted pullulan (GCDPu) was synthesized and used to form nanoparticles for liver-specific drug delivery. GCDPu was characterized by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (¹H NMR). The self-aggregated nanoparticles (GCDPu NPs) with a spherical dimension of about 200 nm were prepared and analyzed by dynamic light scattering (DLS), zeta potential, and transmission electron microscopy (TEM). Doxorubicin (DOX) was selected as an anti-cancer model drug, and the drug-loaded GCDPu NPs were prepared by the emulsion solvent evaporation method. Moreover, the drug encapsulation efficiency (LE%) and loading content (LC%) were determined. Slow DOX release from DOX/GCDPu NPs was confirmed. GCDPu NPs were cytocompatible with Bel-7404 cells and showed high cellular uptake according to the MTT assay, confocal laser scanning microscope (CLSM) and flow cytometry (FCM) results. Compared with free DOX, DOX/GCDPu NPs have exhibited a longer half-life time (t_1/2) and a larger area-under-the-curve (AUC). GCDPu NPs significantly increased DOX contents in the liver and decreased in heart and kidney. Furthermore, DOX/GCDPu NPs exhibited a better anticancer therapeutic effect on tumor-bearing mice. These findings suggest that GCDPu can serve a liver-specific drug delivery system.

Synthesis and characterization of polyethyleneimine-terminated poly(β-amino esters) conjugated with pullulan for gene delivery

Cationic polymers endowed with a flexible system for condensing DNA, are regarded as effective materials for gene delivery. The synthesis of poly(β-amino esters) (pBAEs) based on 1,4-butanediol diacrylate-ethanolamine monomer (1.2:1 molar ratio) and 1,4-butanediol diacrylate-ethylene diamine (1:2 molar ratio) were carried out and modification with 1800 Da polyethyleneimine (PEI) at different weight ratios (3 and 1) as well as conjugation with pullulan in various weight ratios of (0.0625, 0.125, 0.25, and 1) performed. Gel-retardation assay demonstrated that the synthesized polymers were able to condense DNA at low carrier/plasmid (C/P) ratios. The polyplexes with ratio 3 of PEI (pβ₁/PEI₃) were restricted in all C/P ratios and the polyplexes of pβ₁/PEI₃/pull_0.125 were condensed at C/P ratios higher than 0.5. The particle size at C/P were approximately about 200 nm with a positive surface charge. The presence of the pullulan in the structure of the synthesized pBAEs could be effective in reducing toxicity of the base polymer. Highest metabolic activity dedicated to C/P₂ of pβ₂/PEI₃/pull_0.125 with 80.6 percent viability. Furthermore, the most efficient gene reporter delivery was seen at C/P ratio of 6 in pβ₂/PEI₃/pull_0.125 nanoparticles. Therefore, pullulan grafting could enhance the cellular response of cells in terms of cytotoxicity and transfection efficiency.

A Guide to Polysaccharide-Based Hydrogel Bioinks for 3D Bioprinting Applications

Three-dimensional (3D) bioprinting is an innovative technology in the biomedical field, allowing the fabrication of living constructs through an approach of layer-by-layer deposition of cell-laden inks, the so-called bioinks. An ideal bioink should possess proper mechanical, rheological, chemical, and biological characteristics to ensure high cell viability and the production of tissue constructs with dimensional stability and shape fidelity. Among the several types of bioinks, hydrogels are extremely appealing as they have many similarities with the extracellular matrix, providing a highly hydrated environment for cell proliferation and tunability in terms of mechanical and rheological properties. Hydrogels derived from natural polymers, and polysaccharides, in particular, are an excellent platform to mimic the extracellular matrix, given their low cytotoxicity, high hydrophilicity, and diversity of structures. In fact, polysaccharide-based hydrogels are trendy materials for 3D bioprinting since they are abundant and combine adequate physicochemical and biomimetic features for the development of novel bioinks. Thus, this review portrays the most relevant advances in polysaccharide-based hydrogel bioinks for 3D bioprinting, focusing on the last five years, with emphasis on their properties, advantages, and limitations, considering polysaccharide families classified according to their source, namely from seaweed, higher plants, microbial, and animal (particularly crustaceans) origin.

Microorganism-derived biological macromolecules for tissue engineering

According to literature, certain microorganism productions mediate biological effects. However, their beneficial characteristics remain unclear. Nowadays, scientists concentrate on obtaining natural materials from live creatures as new sources to produce innovative smart biomaterials for increasing tissue reconstruction in tissue engineering and regenerative medicine. The present review aims to introduce microorganism-derived biological macromolecules, such as pullulan, alginate, dextran, curdlan, and hyaluronic acid, and their available sources for tissue engineering. Growing evidence indicates that these materials can be used as biological material in scaffolds to enhance regeneration in damaged tissues and contribute to cosmetic and dermatological applications. These natural-based materials are attractive in pharmaceutical, regenerative medicine, and biomedical applications. This study provides a detailed overview of natural-based biomaterials, their chemical and physical properties, and new directions for future research and therapeutic applications.